To understand oneness you need to look things from holistic view and realize that all is one. You need to realize that the basic ingredients of all (human, plants, etc) creation are from five elements – earth, fire, water, sky, air (in sanskrit they call it as panch-a-bhutam!) – and this is scientifically accepted.
Let me illustrate this oneness, unity among diversity, with few examples. Say I have a gold bar. I can take some portion of gold and shape it as a ring or a chain or a bangle. Now we no more call them as gold, but still we realize they (ring/chain/bangle) are originated from the gold bar but taken different shape or identity. Similar example would be sea. When you fill a bucket with water from sea, you cannot call it as sea but you cannot deny the fact it is originated from sea.
If we have blood relation we love each other, if from same caste or religion we show our affection to each other. Then why not to show love and kindness when we are from one origin or made of same ingredients. Advocating oneness would naturally make you feel this way – its the ONLY road to peace!
